Apparatus for determining the water content of liquids and gases

ABSTRACT

Apparatus for the quantitative determination of small amounts of water in liquids and gases by titration of the methanol extract or solution in methanol with Karl Fischer reagent to an end point which is detected using a &#39;&#39;&#39;&#39;dead stop&#39;&#39;&#39;&#39; indicator.

United States Patent Hadermann et al.

[451 Ma-y27, 1975 APPARATUS FOR DETERMINING THE WATER CONTENT OF LIQUIDS AND GASES Inventors: Albert F. Hadermann, Rt. 1,

ljamsville, Md. 21754; Paul F. Waters, 3318 45th St. N.W., Washington, DC. 20016 Filed: Aug. 1, 1973 Appl. No.: 384,563

US. Cl. 23/253 R; 23/259 Int. Cl. G0ln 31/16; GOln 33/18;

' GOln 33/28 Field of Search 23/253 R, 259

[56] References Cited UNITED STATES PATENTS 2,928,782 3/1960 Leisey 23/253 R UX 2,999,673 9/1961 Kessler 23/253 R X Primary Examiner-Robert M. Reese Attorney, Agent, or Firm-Joseph P. Nigon [57] ABSTRACT Apparatus for the quantitative determination of small amounts of. water in liquids and gases by titration of the methanol extract or solution in methanol with Karl Fischer reagent to an end point which is detected using a dead stop indicator.

3 Claims, 2 Drawing Figures APPARATUS FOR DETERMINING THE WATER CONTENT OF LIQUIDS AND GASES BACKGROUND OF THE INVENTION The quantitative determination of the water present in liquids and gases is important in several industrial applications. Even very small quantities of water can cause problems in lubricating oils, aviation fuels and transformer oils for example.

Many methods for the determination of water have been developed. Most of these processes involve fairly sophisticated equipment and are performed by skilled analytical chemists in well equipped laboratories.

BRIEF DESCRIPTION OF THE INVENTION We have developed an improved apparatus for the quantitative determination of small amounts of water present in liquids and gases by titration with Karl Fischer reagent.

Broadly speaking the determination is performed on a methanol extract or solution of the material to be tested. The water is extracted into or dissolved in the methanol along with the sample. The water in the methanol is titrated to an end point using a conventional dead stop indicator. The apparatus is constructed of inert bar stock material and the dead stop circuit is of conventional design.

Our apparatus consists of upper and lower cylindrical cells provided with ring seals to prevent leakage of atmospheric moisture into the titration cell. The upper chamber is filled with a drying agent to insure that air entrying the titration cell upon withdrawal of the fluid content is dry. The lower chamber serves as a vessel within which the titration with the Karl Fischer reagent is performed and is fitted with a removal stirring rotor. The rotor is coated with an inert material, and is located between one fixed and one removable pivot. The end point of the titration is detected by a dead-stop technique that employs two platinum electrodes submerged in the cell contents. Apertures in the body of the chamber wall serve as ducts for sample entry, reagent entry and for filling and emptying the cell contents.

DISCUSSION OF THE DRAWINGS The invention is best appreciated with reference to the drawings in which:

FIG. 1 is a partially disassembled view of the apparatus.

FIG. 2 is a schematic diagram of the support base for the apparatus shown in FIG. 1.

Referring now to FIG. 1, the entire apparatus is constructed from a piece of round bar stock such as Teflon which is chemically inert to most ordinary substances.

FIG. 1 represents a partially disassembled view of the improved apparatus in which the Teflon cap, 1, is provided with a Teflon O ring, 2, which assures a gas tight seal with the inside diameter of the compartment, 3, which is filled with a suitable drying agent, e.g. Drierite." The bottom portion of compartment, 3, is provided with a Teflon O ring, 4, which assures a gas tight seal with the inside diameter of the titration cell, 5. All air passing into the titration cell must pass through vent, 6, and then through the drying agent in compartment, 3, before entering the interior of the titration cell through vent 7. The interior of the titration cell, 5, is provided with a ledge, 8, used as a support for chamber. The brace, 9, is force-fit to rest inside the chamber and on top of the ledge, 8. The brace, 9, may be readily removed freeing the rotor assembly for disassembly and cleaning. The bottom of the titration cell chamber is slanted at a slight angle toward the center of the cell to permit free drainage of the cell contents through port, 13, and out of the stainless steel hypodermic-type, i.e., 20 gauge nipple, 14, which is connected to Teflon capillary tubing and a suitable pump or syringe.

The initial methanol charge for the titration cell chamber is introduced through nipple, 14. Port, l5, communicates with nipple, 16, and the measured amount of sample is introduced into the methanol within the titration cell chamber through Teflon capillary tubing attached to said nipple. The sample may be introduced through the nipple, 16, by delivery from any one of many sundry devices including conventional syringes, tuberculin syringes, or microliter-range syringes. The volume of the sample delivered may be measured volumetrically or the syringe may be weighed before and after delivery of the sample to the titration cell chamber. The Karl Fischer reagent is introduced through the nipple, 17, and out into the titration cell at port, 18, by delivery from any one of many sundry devices including conventional syringes, tuberculin syringes or microliter-range syringes, conventional burets or drying-agent-protected refillable burets fitted with a stainless steel nipple for connection to Teflon capillary tubing. Platinum electrodes, 19, are connected to a conventional dead-stop indicator circuit.

The operation of the apparatus is as follows: An appropriate quantity of methanol is introduced into the titration cell chamber through port 13, and Karl Fischer reagent is introduced through port 18, until the current shown at the indicator of the dead-stop circuit shows that excess iodine now exists in the methanol within the titration cell. The original water content of the methanol has now been blanked out by reaction with Karl Fischer reagent and the Karl Fischer reagent may now be standardized by introducing a sample of methanol containing a known quantity of water through port, 15. The titration procedure is repeated and the titer of the Karl Fischer reagent is determined. Measured amounts of samples are now introduced through port 15 and the water contents are determined to titration to a dead-stop.

FIG. 2 shows a schematic diagram of the support base of the apparatus shown in FIG. 1. An alternating magnetic field is generated between the upright posts, 21, of a U-shaped ferromagnetic member, 22, wound with magnet-wire 23, and connected to a variable frequency 6 volt power supply (not shown), at the ends of the winding, 24. The base is provided with posts, 25, so that the titration cell assembly may fit snuggly between four posts when lowered onto the upper surface of the base plate, 26, of the magnetic driver assembly.

The apparatus shown in FIGS. 1 and 2 may be scaled in size to cover a size range extending from a titration cell volume of one ml to 500 ml and hence can be used to determine the moisture content of extremely small quantities of expensive materials.

The apparatus may be made of glass, Teflon, high density polyethylene, polypropylene etc.

What is claimed is:

l. An apparatus for determining the water content of a liquid or gas which consists essentially of upper and lower cylindrical cells provided with Teflon O ring seals to prevent the leakage of atmospheric moisture llflIO the titration cell; the upper chamber being filled with a drying agent to ensure that air entering the titration cell upon withdrawing the fluid contents is dry; the lower chamber serving as a vessel within which the titration with Karl Fischer Reagent is performed and being fitted with a removable stirring rotor, clad with an inert protective material located between one fixed ind one removable pivot; provision for detecting the and point of the titration by a dead-stop technique employing two platinum electrodes in communication with the cell contents; access to the lower chamber being provided by apertures in the body of the chamber wall and fitted with nipples for connection to tubing. for connection to said nipples and serving as ducts for sample entry, reagent entry and for filling and emptying the cell contents without complete disassembly.

2. The apparatus according to claim 1 wherein the apertures in the lower chamber are fitted with 20 gauge stainless steel hypodermic needle nipples 3. The apparatus according to claim 2 wherein the hypodermic needle nipples are connected to inert, e.g. Teflon tubing of 0.020 inch inside diameter with 0.010

inch wall thickness. 

1. AN APPARATUS FOR DETERMINING THE WATER CONTENT OF A LIQUID OR GAS WHICH COMSISTS ESSENTIALLY OF UPPER AND LOWER CYLINDRICAL CELLS PROVIDED WITH TEFLON "O" RING SEALS TO PREVENT THE LEAKAGE OF ATMOSPHERIC MOISTURE INTO THE TITRATION CELL; THE UPPER CHAMBER BEING FILLED WITH A DRYING AGENT OT ENSURE THAT AIR ENTERING THE TITRATION CELL UPON WITHDRAWING THE FLUID CONTENTS IS DRY; THE LOWER CHAMBER SERVING AS A VESSEL WITHIN WHICH THE TITRATION WITH KARL FISCHER REAGENT IS PERFORMED AND BEING FITTED WITH A REMOVABLE STIRRING ROTOR, CLAD WITH AN INERT PROCTETIVE MATERIAL, LOCATED BETWEEN ONE FIXED AND ONE REMOVABLE PIVOT; PROVISION FOR DECTING THE END POINT OF THE TITRATION BY A "DEAD-STOP" TECHNIQUE EMPLOYING TWO PLATINUM ELECTRODES IN COMMUNICATION WITH THE CELL CONTENTS; ACCESS TO THE LOWER CHAMBER BEING PROVIDED BY APERTURES IN THE BODY THE CHAMBER WALL AND FITTED WITH NIPPLES FOR CONNECTION TO TUBING, FOR CONNECTION TO SAID NIPPLES AND SERVING AS DUCTS FOR SAMPLE ENTRY, REAGENT ENTRY AND FOR FILLING AND EMPTYING THE CELL CONTENTS WITHOUT COMPLETE DISASSEMBLY.
 2. The apparatus according to claim 1 wherein the apertures in the lower chamber are fitted with 20 gauge stainless steel hypodermic needle nipples.
 3. The apparatus according to claim 2 wherein the hypodermic needle nipples are connected to inert, e.g. Teflon tubing of 0.020 inch inside diameter with 0.010 inch wall thickness. 